Method and device for cleaning the atmosphere

ABSTRACT

Method for treating atmospheric pollutants by contacting the atmosphere with a catalyst composition or adsorptive material coated on the surface of a substrate, preferably a motor vehicle radiator, in which the catalyst composition, preferably including a base metal, precious metal, or salts/oxides thereof, or adsorptive material, preferably including a zeolite, Group IIA alkaline earth metal oxide or carbon, is protected from degradation by harmful contaminants such as solid or aerosol particulates, water, SOx, NOx and water borne salts contained in the atmosphere by a coating of at least one porous protective material and a device useful therefor.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of application Ser. No. 09/456,016filed Nov. 30, 1999, now U.S. Pat. No. 6,190,627.

FIELD OF THE INVENTION

The present invention relates to a method for the low temperaturecleaning of the atmosphere and more particularly to the rendering of theouter surface of a substrate, such as a radiator of a motor vehicle,capable of either catalytically converting atmospheric pollutants toless harmful materials or adsorbing such pollutants without adverselyaffecting the functioning of the substrate. The method is accomplishedthrough the employment of a pollutant treatment coating on the surfaceof such substrate said coating being further provided with anovercoating of either a protective material alone or in combination witha water repellant material which improves durability and long termperformance of the catalytic or adsorptive coating.

BACKGROUND OF THE INVENTION

A review of literature relating to pollution control reveals that thegeneral approach is to reactively clean waste streams entering theenvironment. If too much of one pollutant or another is detected orbeing discharged, the tendency has been to focus on the source of thepollutant. For the most part gaseous streams are treated to reduce thepollutants prior to entering the atmosphere.

It has been disclosed to treat atmospheric air directed into a confinedspace to remove undesirable components therein. However, there has beenlittle effort to treat pollutants which are already in the environment;the environment has been left to its own self-cleansing systems.

References are known which disclose proactively cleaning theenvironment. U.S. Pat. No. 3,738,088 discloses an air filtering assemblyfor cleaning pollution from the ambient air by utilizing a vehicle as amobile cleaning device. A variety of elements are disclosed to be usedin combination with a vehicle to clean the ambient air as the vehicle isdriven through the environment. In particular, there is disclosedducting to control air stream velocity and direct the air to variousfilter means. The filter means can include filters and electronicprecipitators. Catalyzed postfilters are disclosed to be useful to treatnon-particulate or aerosol pollution such as carbon monoxide, unburnedhydrocarbons, nitrous oxide and/or sulfur oxides, and the like.

Another approach is disclosed in U.S. Pat. No. 5,147,429. There isdisclosed a mobile airborne air cleaning station. In particular thispatent features a dirigible for collecting air. The dirigible has aplurality of different types of air cleaning devices contained therein.The air cleaning devices disclosed include wet scrubbers, filtrationmachines, and cyclonic spray scrubbers.

The difficulty with devices disclosed to proactively clean theatmospheric air is that they require new and additional equipment. Eventhe modified vehicle disclosed in U.S. Pat. No. 3,738,088 requiresducting and filters which can include catalytic filters.

DE 40 07 965 C2 to Klaus Hager discloses a catalyst comprising copperoxides for converting ozone and a mixture of copper oxides and manganeseoxides for converting carbon monoxide. The catalyst can be applied as acoating to a self-heating radiator, oil coolers or charged-air coolers.The catalyst coating comprises heat resistant binders which are also gaspermeable. It is indicated that the copper oxides and manganese oxidesare widely used in gas mask filters and have the disadvantage of beingpoisoned by water vapor. However, the heating of the surfaces of theautomobile during operation evaporates the water. In this way,continuous use of the catalyst is possible since no drying agent isnecessary.

Responsive to the difficulties associated with devices which proactivelytreat the atmosphere, the Assignee herein in U.S. patent applicationSer. No. 08/410,445 filed on Mar. 24, 1995, now abandoned, U.S. patentapplication Ser. No. 08/589,182 filed Jan. 19, 1996, now abandoned, andU.S. patent application Ser. No. 08/589,030 filed Jan. 19, 1996, nowU.S. Pat. No. 6,200,542, each incorporated herein by reference,disclosed apparatus in related methods for treating the atmosphere byemploying a moving vehicle. In preferred embodiments a portion of thesurface of the engine or cabin cooling system (e.g. the radiator,air-conditioning condenser, etc.) is coated with a catalytic oradsorption composition. Additionally, the fan associated with the enginecooling system can operate to draw or force air into operative contactwith the radiator. Pollutants contained within the air such as ozone,hydrocarbons and/or carbon monoxide are then catalytically converted tonon-polluting compounds (e.g., oxygen, water and carbon dioxide).

The Assignee herein also has pending U.S. patent application Ser. No.08/412,525 filed on Mar. 29, 1995, now abandoned, incorporated herein byreference, which discloses devices and methods for proactively treatingthe atmosphere catalytically by employing a stationary object such asselected surfaces of an automobile at rest, a billboard, an airconditioning unit and the like coated with a catalytic composition.

In addition, International Publication No. WO 98/02235 of the Assigneeherein discloses a process of catalytically activating the surface of aheat exchange device such as a motor vehicle radiator while retainingthe heat exchange properties of the device. The method enables thecatalytic treatment of the atmosphere by converting pollutants containedtherein to less harmful materials while allowing the radiator to performits function normally. A polymeric protective coating which is stable upto temperatures of about 100° C. may be employed to retard degradationand inactivation of the catalyst.

The application of a catalyst or absorbent composition to the surface ofa substrate such as a radiator of a motor vehicle presents problems suchas the exposure of the composition to relatively high concentrations ofcontaminants which can deleteriously affect the functioning of thecomposition. Such contaminants include solid or vaporized particulates,corrosive compounds such as salts and oxides of nitrogen, sulfur and thelike. Contact of the composition with such contaminants can result inmasking, fouling and/or poisoning. In addition, water (and contaminantscontained therein) can be a source of degradation and can also decreasethe activity and useful life of catalyst and adsorbent compositions.

It would therefore be a significant advance in the art of reducingatmospheric pollution to employ catalytic and adsorptive compositioncoated devices for the treatment of the atmosphere to remove pollutantscontained therein wherein the composition is protected against thosecontaminants commonly encountered in the atmosphere which can adverselyaffect performance of the composition. It would be a further advance inthe art if the composition could be protected from contaminants at fromambient temperatures up to about several hundred degrees centigrade. Itwould be still a further advance in the art if the composition could beprotected from water especially liquid water.

SUMMARY OF THE INVENTION

The present invention generally relates to a method and device forcleaning the atmosphere by removing pollutants therefrom. A surfacewhich contacts the atmosphere such as a surface of a radiator of a motorvehicle is treated with a catalyst or absorbent composition so that theouter surface (i.e., air side) thereof is capable of either adsorbingpollutants or catalytically converting pollutants contained in theatmosphere into less harmful substances. The composition is coated atleast in part (preferably completely) with a porous, protective coatingas defined herein which effectively protects the composition fromatmospheric contaminants at ambient temperatures up to several hundreddegrees centigrade or higher. Preferably, the porous protective coatingis itself overcoated with a hydrophobic material. The present inventionalso encompasses devices treated in the manner described herein.

The term “adsorption” is defined as including: (a) the penetration ofone substance into the inner structure of another (commonly referred toas “absorption”); and (b) adherence of the atoms, ions, or molecules ofa gas or liquid to the surface of another substance (commonly referredto as “adsorption”). See, for example, Hawley's Condensed ChemicalDictionary, Thirteenth Edition, Van Nostrand Reinhold, 1997, pp. 2, 3,24.

Similarly, related terms such as, for example, adsorbents, adsorbing,adsorptive, etc. shall be understood to include both related meanings.The term “atmosphere” means the mass of air surrounding the earth, andincludes “ambient air” which is the portion of the atmosphere that isdrawn or forced towards the outer surface of the coated substrate.Ambient air includes air, which has been heated either incidentally orby a heating means. The term “substrate” is used in its customary broadsense and includes any surface which can be coated with a suitablecatalyst or adsorbing composition and thereafter have the compositionprotected in the manner described herein. Such surfaces include thosesurfaces found in motor vehicles such as automobiles, trucks, vans,buses, trains, airplanes and the like and include but are not limited toradiators, condensers, charge air coolers, transmission coolers,inserted devices which may be separately heated, heat exchangers, fluidtransporting conduits and the like. Surfaces normally described asstationary such as billboards, road signs, outdoor HVAC equipment arealso included. For convenience only, a motor vehicle radiator will bediscussed herein as typical of a suitable substrate.

In accordance with the present invention, the surface of the substrate(e.g., radiator) is provided with a substance which can eithereffectively catalyze the conversion of pollutants contained in theatmosphere to less harmful substances or adsorb such pollutants forlater treatment as appropriate. The surface of the radiator is thereforecapable of either catalytically converting pollutants such ashydrocarbons, carbon monoxide and ozone into less harmful materials suchas oxygen, carbon dioxide and water, or adsorbing pollutants such asNOx, SOx hydrocarbons and carbon monoxide as the case may be.

In one aspect, the present invention is directed to a method ofcatalytically treating the atmosphere to convert pollutants to lessharmful materials comprising treating an outer surface of a substrate,particularly an auto radiator to render said surface capable ofcatalytically converting said pollutants and then providing the catalystwith an overcoating of at least one material or mixtures of suchmaterials which is porous and preferably also adsorbent (hereinafter,“porous protective material”). The porous protective material ispreferably sufficiently porous to enable the atmosphere including thecontained pollutants to be treated to pass therethrough into operativecontact with the catalyst composition to enable conversion thereof intoless harmful materials. The porous protective material preferably shouldalso be adsorbent in order to trap atmospheric catalyst degradatingcontaminants so that they are at least substantially prevented fromreaching the catalyst composition. Still further, the catalyst and theporous protective material are preferably stable at ambient temperaturesand up to about several hundred degrees centigrade.

In another aspect of the invention, the porous protective material mayinclude or be overcoated with at least one substance which is capable ofprotecting the catalyst composition from contact with liquid waterand/or water vapor (hereinafter, “hydrophobic protective material”).

In another aspect of the invention, the outer surface of the substrate(e.g. radiator) is made of or provided with a catalytically activesubstance such as a base metal catalyst (e.g. manganese dioxide),precious metal catalyst or combination thereof. As used herein the terms“base metal catalyst” and “precious metal catalyst” shall include thebase metals and precious metals themselves as well as compoundscontaining the same e.g., salts and oxides and the like.

In another aspect, the present invention is directed to a method forcleaning the atmosphere comprising treating an outer surface of asubstrate, particularly an auto radiator with an adsorptive material torender said surface capable of adsorbing pollutants present in theatmosphere such as NOx, SOx hydrocarbons and carbon monoxide and thenproviding the adsorptive material with an overcoating of at least oneporous protective material.

In another aspect of the invention, the outer substrate surface coatedwith either a catalyst composition or adsorbing composition, is coatedwith the porous protective material which is then overcoated with ahydrophobic protective material. The protective material, whetherporous, hydrophobic or a combination of both still permits pollutants topass into contact with either the catalyst composition so they may beconverted to less harmful materials or into contact with the adsorbingcomposition so that they may be absorbed and thereby removed from theatmosphere.

The coatings contemplated for use herein do not substantially interferewith the normal desired operation of the substrate (e.g., auto radiator)whose surface has been coated.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings in which like reference characters indicate likeparts are illustrative of embodiments of the invention and are notintended to limit the invention as encompassed by the claims formingpart of the application.

FIGS. 1A-1F are cross-sectional views showing various arrangements ofthe catalyst or adsorbing composition and protective material of thepresent invention.

FIG. 2 is a side view of a radiator assembly of a motor vehicle; and

FIG. 3 is an enlarged cross-sectional view of a motor vehicle radiator.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a method of cleaning the atmosphereby treating the surface of a substrate (e.g. a motor vehicle radiator)so that pollutants contained in ambient air upon contact with saidsurface may either be readily converted catalytically to less harmfulmaterials or removed by adsorption. For example, (a) the surface of thesubstrate may be catalytic if the surface is provided with catalyticallyactive materials or a catalyst composition or the surface itself may bemade of a catalytically active material; or (b) an adsorptivecomposition may be applied to the surface of the substrate. Thus, thepresent invention is particularly adapted to either the catalyticconversion of hydrocarbons, ozone and carbon monoxide into less harmfulmaterials such as oxygen, carbon dioxide and water or the removal ofe.g., NOx, SOx, hydrocarbons and carbon monoxide by adsorption. When themethod is directed to catalytic treatment of the atmosphere, the methodis preferably performed at temperatures of from about 0 to about 150° C.

In accordance with the present invention, the surface coat of thecatalyst or adsorptive composition is overcoated with a porousprotective material which is porous and adsorbent. The term “porous”means that the material allows the ambient air containing pollutantssuch as hydrocarbons, ozone, carbon monoxide and the like to passthrough the porous protective material to effectively contact thecatalyst and adsorptive composition and thereby be converted to lessharmful materials. The term “adsorbent” when used herein means thatundesirable contaminants such as particulate matter, high molecularweight hydrocarbons, water borne salts, aerosols, gases (e.g. NOx, SOx),and the like which can mask, foul and/or poison the catalyst compositionor interfere with the functioning of the adsorptive composition areadsorbed, trapped and may be retained in the porous protective materialso that they are maintained out of contact with the underlying activecomposition.

In a further aspect of the present invention, the porous protectivematerial may optionally include or may be overcoated with a hydrophobicmaterial which substantially prevents water (liquid or vapor) fromcontacting the catalytic or adsorptive composition. It has been observedthat in the presence of liquid water and the contaminants that may becontained therein, degradation of the catalyst composition isaccelerated and conversion rates of pollutants to less harmful materialsare more quickly degraded than in the absence of liquid water and thecontained contaminants. It is anticipated that adsorptive compositionswill similarly benefit from protection from water.

In a still further aspect of the invention, the catalytic or adsorptivecomposition coated on the substrate may first be coated with thehydrophobic protective material and the porous protective material iscoated over it.

For reasons of convenience, the invention will be further described andexemplified using its catalytic embodiment. Those skilled in the artwill appreciate that the adsorptive embodiment of the invention can besubstituted and applied and utilized in a substantially similar manneras described for the catalytic embodiment using substantially similartechniques.

The atmosphere contacting surface is the outer surface of any devicesuch as a motor vehicle radiator which can effectively receive thecatalyst composition and overcoat of the protective material(s) andwhich comes into contact with a pollutant-containing gas such as ambientair. Any device in which there is a flow of ambient air thereover ortherethrough may be treated in accordance with the present invention. Ofparticular importance to the present invention is the rendering of theouter surface of the substrate (e.g., radiator) capable of catalyticallyconverting pollutants to less harmful materials without adverselyaffecting the substrate and its function. Thus, if the substrate is aradiator, the catalyst composition and protective material overcoat(s)shall not substantially adversely affect either the heat exchangeproperties or the physical integrity of the radiator. The catalystcomposition is protected by at least one porous, preferably adsorbentprotective material to insure against premature degradation of thecatalyst composition and optionally one hydrophobic protective materialto protect the catalyst composition from water (liquid and/or vapor).The porous protective material and the hydrophobic protective materialmay also be mixed and coated onto the catalyst composition as one layer.

A particular embodiment of the present invention is directed towardsprotective materials and methods for improving the durability ofcatalysts used for treating the atmosphere. Such catalysts include, forexample, ozone converting catalytic compositions (especiallycompositions containing MnO₂), and catalysts useful for treating carbonmonoxide and hydrocarbons as well. Manganese dioxide is a particularlypreferred catalyst material for use in the present invention to treatozone, and precious metals such as platinum and/or palladium arepreferred to treat hydrocarbons and carbon monoxide.

In this embodiment, the invention is specifically directed to the use ofprotective materials which may be overcoated on catalytic systems (e.g.,catalyst coated automobile radiators) which are useful for cleaning theatmosphere by catalytically treating pollutants contained in theatmosphere. The function of the protective materials is to preventatmospheric catalyst degrading contaminants (e.g., solid or aerosolparticulates, water, SOx, NOx, water borne salts, high molecular weighthydrocarbons, etc.) which lead to masking, fouling, and/or poisoning ofthe catalyst composition from interacting with the catalyst composition.Since the purpose of an automobile radiator is to provide heat exchangeand cooling for the engine, the radiator is usually located at the frontof the vehicle where it has ample access to large volumes of ambientair. As a result, the radiator operates in a relatively dirtyenvironment and is exposed to all types of solid, gaseous and liquidairborne and roadway contaminants. A catalyst composition applied to theradiator for purposes of treating atmospheric pollutants such as ozoneshould preferably be able to function over an extended period of time ina severely dirty environment. Long term road tests of ozone destructioncatalysts applied to automobile radiators have shown that deactivationof catalyst performance occurs over time as the mileage on the vehicleincreases. Visual inspection of prior art radiators which had beensurface coated only with an ozone catalyst, e.g., a MnO₂ containingcatalyst and removed from service after extended on-road aging (e.g.,50,000 or 100,000 miles) showed the readily apparent deposition of dirt,salts, and other solid contaminants on the surface of the catalystcomposition. These unprotected compositions suffered a significant lossof activity measured at about 50% or higher. Chemical analyses alsoconfirmed the deposition of sulfate, sodium, chloride, calcium, silica,alumina and carbon on the catalyst composition. Although many mechanismsmay exist for deactivation of such road-aged catalysts, it is believedthat deposition of atmospheric contaminants (particularly SOx aerosols,and particulate matter both large and small) account for a significantdecrease in catalyst performance over time.

The practice of the methods of the present invention minimize contact ofairborne contaminants with the radiator catalyst composition. This isaccomplished by applying an overcoat of a porous, preferably adsorbentprotective material on the surface of the catalyst composition. Thefunction of the porous protective material is to trap and hold airborneparticulates, high molecular weight hydrocarbons, aerosols, water bornesalts and catalyst deactivating gases such as SOx, so that they do notcome into contact with the active catalyst composition underneath. Theporous protective material is preferably dense enough to trapcontaminants but also porous enough to allow free passage of the ambientair which contains the pollutant to be treated (e.g. ozone,hydrocarbons, carbon monoxide) to the catalyst composition below. Inthis way, the catalyst composition is kept substantially contaminantfree and is therefore able to provide high levels of long lastingpollutant conversion.

Suitable porous protective materials may include, but are not limited tozeolites, clays, alumina, silica, alkaline earth oxides, rare earthoxides, carbon, inert metal oxides as well as mixtures thereof.

The zeolites for use in the present invention as the protective materialinclude acid and/or ion exchanged and/or dealuminated zeolites examplesof such zeolites include but are not limited to zeolite-Y, ferrierite,zeolite-A, beta-zeolite, ZSM-5, other molecular sieves and mixturesthereof.

Clays include, for example, attapulgite, kaolin and mixtures thereof.

Aluminas include, silica alumina, gamma alumina, alpha alumina,colloidal alumina, and mixtures thereof including those having high andlow surface areas.

Typical useful silicas include silicalite, silica gel, fumed silica,aerogels, high silica content silica-aluminas, colloidal silica andmixtures thereof.

Examples of useful alkaline earth oxides include calciumoxide/hydroxide, calcium magnesium aluminates, barium carbonate, bariumoxide/hydroxide, strontium carbonate, strontium oxide/hydroxide, spinelsand mixtures thereof.

Typical and useful rare earth oxides include ceria, lanthana andmixtures thereof.

Examples of carbon for use in the present invention include granularactivated carbon, carbon black, permanganate on carbon and mixturesthereof.

In addition to the examples mentioned above inert metal oxides such as,for example, titania, zirconia, silica, and mixtures thereof can beemployed as the protective material.

The preferred porous protective material for use in the practice of theinvention is aluminum oxide, more preferred is high surface area silicacontaining aluminum oxide

Protective materials may optionally also be combined with and mayinclude hydrophobic substances which render the area around the catalystcomposition water repellant. The hydrophobic material may also beprovided as a separate overcoat either over or under the porouscomponent. Suitable hydrophoblic substances for use in the presentinvention include, but are not limited to water dispersible polymers,polymer emulsions such as fluoropolymer water based latex emulsions(FC-824 and FC-808 manufactured by 3M Company) and water based TEFLONemulsions (e.g. TF5035 manufactured by 3M Company), and siliconepolymers, such as water based silicone emulsions (e.g. BS-1306 andBS-1001A manufactured by Wacker Silicones Corp.). The protectivematerial, as more fully explained hereinafter, may be applied by anynumber of methods such as dipping or spraying a slurry containing theprotective material. The porous protective material and the optionalhydrophobic protective material may each be applied in separate layersto the catalytic surface or they may be applied as a mixture.

The protective material may be employed to cover a variety of catalystcompositions. As previously indicated, such catalyst compositionsinclude base metals, precious metals, salts and oxides thereof andcombinations thereof. Manganese dioxide is an especially preferredcatalytic material especially for the conversion of ozone. It is alsoanticipated that manganese dioxide will itself be useful as the porousprotective material for overcoating and protecting catalyst coatingswhen practicing the catalytic embodiment of the invention.

The base metals which may be employed for the catalyst compositioninclude all base metals which can effectively convert ozone to oxygenand/or carbon monoxide to carbon dioxide. The preferred base metalsinclude manganese, iron, copper, chromium, and zinc compounds containingthe same and combinations thereof. The base metals are typically used inthe form of oxides.

The precious metals are preferably selected from those customarily usedin catalyst compositions for the purification of engine exhaust, e.g.,platinum, palladium, rhodium and mixtures thereof. Silver and gold mayalso be used.

The catalyst composition may also be provided with a suitable supportmaterial which preferably has a high surface area. The preferred supportmaterials are refractory oxides such as those selected from the groupconsisting of ceria, alumina, titania, silica, zirconia, and mixturesthereof with alumina being the most preferred refractory oxide support.It is preferred that the refractory oxide support have a high surfacearea to maximize the amount of the catalytic material within a givenunit area. The term “high surface area” as it pertains to the refractoryoxide support shall generally mean that the surface area of the supportis at least 100 m²/g preferably in the range of from about 100 to 300m²/g.

The catalyst composition may be applied to the radiator surface bytechniques commonly used in the industry, e.g., dipping and/or spraying.

The catalyst compositions described above once deposited or made part ofthe substrate are then protected with at least one protective material,preferably, a porous material having adsorbent properties and mixturesthereof as described above. The porous protective material may be in theform of a single layer or multiple layers lying between the catalystcomposition and the atmospheric airflow containing the pollutants whichare to be treated. The same or different protective materials may beused for the multiple layer configuration optionally including one ormore layers of a hydrophobic protective material as describedpreviously. For example, the catalyst composition as deposited on thesurface of the substrate may be overcoated with one or more layers of aporous protective material such as alumina with the alumina coatingoptionally having one or more layers of a hydrophobic protectivematerial (e.g. latex based emulsion) coated thereover.

In an alternative embodiment, the protective materials may encapsulatethe catalyst composition. Such encapsulated catalyst compositions may beprepared by coating individual particles of the catalyst composition bydipping or spraying with a slurry containing one or more protectivematerials, e.g., the porous protective material and/or the hydrophobicprotective material.

In operation of the present invention, ambient air is drawn or forcedover the catalytic surface by natural wind currents or by air drawingdevices such as fans. For land use motor vehicles, the radiator surfacesare preferably the surfaces which are coated with the catalystcomposition, and the air drawing device is the motor vehicle radiatorfan. It should be understood, however, that other substrates such as airconditioning condensers, charge air coolers, transmission coolers,inserted devices which may be separately heated and the like may betreated in a like manner.

In a preferred embodiment of the present invention, the atmospherecontacting surfaces are appropriate surfaces of a motor vehicleradiator, particularly in automobile radiator. By treating the radiatorsurface as described herein pollutants can be readily removed from theatmosphere while the catalyst is able to maintain useful conversionrates for extended periods of time. The normal function of the radiatoris not substantially affected by the coating(s).

The present invention will be better understood by those skilled in theart by reference to accompanying FIGS. 1-3. What is particularlyimportant in accordance with the present invention is that the catalystcomposition is protected from degrading contaminants by the applicationof at least one protective material as described herein. As the ambientair encounters the catalytic surface of e.g., the radiator,hydrocarbons, carbon monoxide and/or ozone are catalytically reacted toproduce less harmful materials such as oxygen, carbon dioxide, and watervapor. Additionally, gaseous contaminants such as high molecular weighthydrocarbons, SOx and NOx and other contaminants such as dirt, carbon,aerosols, particulates, water, water borne salts, soil and the like arekept away from the catalyst composition through the use of theprotective material(s).

It will be appreciated by those skilled in the art that when thesubstrate is associated with a vehicle, any suitable vehicle can beemployed. Vehicles include cars, trucks, trains, boats, ships,airplanes, dirigibles, balloons, and the like. Preferably in a motorvehicle, the atmosphere contacting surfaces are surfaces located towardthe front of the vehicle in the vicinity of the cooling system fan.Useful contact surfaces include the outside (i.e. airside) surfaces ofthe radiator, air conditioner condenser, and the like which are alllocated and supported within the housing of the vehicle.

In a preferred embodiment of the invention the protective materialincludes a hydrophobic substance which functions to protect the catalystcomposition from liquid water and/or water vapor. The hydrophobicprotective material is preferably applied as a separate layer or layerseither directly over the porous protective overcoat coated on thecatalyst composition or indirectly thereover (i.e. wherein thehydrophobic protective material coating layer is between the catalystcomposition surface coating and the porous protective material layer).As an alternative, the hydrophobic substance may be incorporated intoone or more porous protecting material coating layers, or may be used inconjunction with one or more other protective materials to encapsulatethe catalyst and/or adsorbent composition prior to coating the support.The hydrophobic substance may also be used as the only protectivematerial to overcoat the catalyst or adsorptive substrate coating.

The hydrophobic protecting material can prevent liquid water and/orwater vapor from contacting the catalyst composition and is at least tosubstantially stable under the temperature conditions typicallyassociated with a substrate such as a motor vehicle radiator. Thehydrophobic protecting material will be stable at temperatures fromabout 0 to 300° C. preferably 0 to 200° C., more preferably 0 to 150° C.and most preferably 0 to

Various arrangements of the protective material optionally including ahydrophobic substance and the catalyst composition are shown in FIGS.1A-1E. Although single overcoats of the porous and hydrophobicprotective coatings and the components thereof are depicted in theFigures, it will be appreciated that multiple coats either alternatingor continuous are also within the scope of the invention.

Referring to FIG. 1A there is shown a first arrangement in accordancewith the present invention in which a substrate 100, such as a radiator,is coated with a catalyst or adsorptive (collectively hereinafter,“active”) composition layer 102 and a coating layer 104 thereovercomprising a porous, adsorbent material such as alumina, silica ormixture thereof.

The present invention may optionally provide for a hydrophobic layer asdescribed previously. Referring to FIGS. 1B-1D and first to FIG. 1B, thehydrophobic layer 106 is placed above the coating layer 104. Thehydrophobic layer 106 provides water repellency to the substrate andthereby prevents water from adversely affecting the active composition.

In an alternative embodiment, the hydrophobic layer 106 is placedbetween the coating layer 104 and the active composition 102 as shown inFIG. 1C. In a still further embodiment the protective material (e.g.alumina) used for the coating layer 104 and the hydrophobic material(e.g. polymeric silicones or fluoropolymers) are combined into a singlelayer 108 as shown specifically in FIG. 1D.

In a further alternative embodiment individual particles of the activecomposition are encapsulated by the protective material as shown inFIGS. 1E and 1F typically by spray drying the particles with theprotective material. Such spray drying techniques are well known in theart. In particular as shown specifically in FIG. 1E the substrate 100has thereon one or more layers 120 comprised of encapsulated particles122 which, as shown in FIG. 1F are comprised of the active composition102 with at least one protective layer 104 thereover optionally with atleast one layer 106 of a hydrophobic substance.

The application of the active composition and protective materials isdescribed with reference to FIGS. 2 and 3. A radiator assembly 20 of amotor vehicle is shown in FIG. 2 including a housing 10, a grille 12, anair conditioner condenser 14, a radiator 16 and a radiator fan 18. Itwill be understood that other vehicle components are typically found ina motor vehicle.

Referring to FIG. 2, the preferred atmosphere contacting surfacesinclude the air side tube 13 and fin 15 surfaces of the air conditioningcondenser 14, as well as the air side tube 17 and fin 19 surfaces of theradiator 16. These surfaces are located within the housing 10 of a motorvehicle. They are typically under the hood of the motor vehicle betweenthe front of the vehicle and the engine. The air conditioner condenser14 and the radiator 16 can be directly or indirectly supported by thehousing 10 of the vehicle.

The surfaces 13, 15 and 17, 19 of the air conditioner condenser 14 andthe radiator 16, respectively can be treated in accordance with thepresent invention to provide a catalytic or adsorptive surface coveredwith a protective material as described above in connection with FIGS.1A-1E. The most preferred atmosphere contacting surface is the outersurface of the radiator 16. A typical radiator has front and rearsurfaces with spaced apart flat tubes having therebetween a plurality ofradiator corrugated plates. More specifically and referring to FIG. 3,there is shown a radiator 16 including spaced apart tubes 40 for theflow of a first fluid and a series of corrugated plates 42 therebetweendefining a pathway 44 for the flow of a second fluid transverse to theflow of the first fluid. The first fluid such as antifreeze is suppliedfrom a source (not shown) to the tubes 40 through an inlet 46. Theantifreeze enters the radiator 16 at a relatively high temperaturethrough the inlet 46 and eventually leaves the radiator through anoutlet 48. The second fluid such as air passes through the pathway 44and thereby comes into heat exchange relationship with the first fluidpassing through the tubes 40.

In accordance with the present invention, the surfaces of the corrugatedplates 42 of the radiator 16 can be treated to provide a catalytic oradsorptive surface which is protected from contaminants includingparticulate matter, gases, water and the like.

As previously discussed, another embodiment of the invention isspecifically directed to the use of protective materials which may beovercoated on adsorptive systems (e.g., automobile radiators coated withadsorptive compositions) which are useful for cleaning the atmosphere byadsorbing pollutants particularly hydrocarbons contained in theatmosphere. The function of the protective materials is to preventadsorptive material degrading contaminants present in the atmosphere (inparticular solid or aerosol particulates, water, water borne salts andhigh molecular weight hydrocarbons) which would lead to masking,fouling, and/or poisoning of the adsorptive composition from interactingwith the adsorptive material. Since the purpose of an automobileradiator is to provide heat exchange and cooling for the engine, theradiator is usually located at the front of the vehicle where it hasample access to large volumes of ambient air. As a result, the radiatoroperates in a relatively dirty environment and is exposed to all typesof solid, gaseous and liquid airborne and roadway contaminants. Anadsorptive material applied to the radiator for purposes of adsorbingatmospheric pollutants such as hydrocarbons and carbon monoxide shouldpreferably be able to function over an extended period of time in aseverely dirty environment.

The practice of the methods of the present invention minimize contact ofairborne contaminants with the radiator adsorptive composition. This isaccomplished by applying an overcoat of a porous, preferably adsorbentprotective material on the surface of the adsorptive composition. Thefunction of the porous protective material is to trap and hold airborneparticulates, aerosols, water borne salts and high molecular weighthydrocarbons so that they do not come into contact with the adsorptivematerial underneath. The porous protective material is preferably denseenough to trap contaminants but also porous enough to allow free passageof the ambient air which contains the pollutant to be treated (e.g.,hydrocarbons, carbon monoxide) to the adsorptive composition below. Inthis way, the adsorptive composition is kept substantially contaminantfree and is therefore able to provide high levels of long lastingpollutant adsorption. Useful and preferred adsorptivematerials/compositions include zeolites such as acid and/or ionexchanged and/or dealuminated zeolites examples of such zeolites includebut are not limited to zeolite-Y, ferrierite, zeolite-A, beta-zeolite,ZSM-5, other molecular sieves and mixtures thereof; carbon and Group IIAalkaline earth metal oxides such as calcium oxide. The adsorbedpollutants may be subsequently collected, if desired, by desorption, forexample, followed by destruction by catalytic reaction or incineration.

EXAMPLE 1

A Ford TAURUS automobile radiator was coated in four separate sections(“quadrants”) with four MnO₂ based ozone destroying catalystformulations. A brief description of each formulation is given below:

Section 1: same as Section 2 formulation without the alumina coating.

Section 2: 3.5 μm average particle size MnO₂ coating containing asilicone/acrylic binder blend and overcoated with an SRS-II aluminacoating.

Section 3: 3.5 μm particle size reference MnO₂ coating prepared from anunstable (i.e. coagulated) slurry formulation.

Section 4: 1 μm average particle size MnO₂ coating containing an acrylicbinder without the alumina overcoat.

The MnO₂ binder system used in the Section 1 and 2 formulationscontained a 3:1 blend of acrylic/styrene acrylic latex binder (RHOPLEXP-376 binder from Rohm & Haas) with a reactive silicone latex binderresin (M-50E from Wacker Silicones Corp.). The MnO₂ binder system usedin the non-preferred reference Section 3 formulation contained an EVA(ethylene vinyl acetate) latex binder from National Starch (DUROSETE-646 binder). The MnO₂ binder system used in the Section 4 formulationcontained an acrylic latex binder from National Starch (NACRYLIC X-4280binder). The SRS-II alumina binder system used in the overcoatformulation coated on Section 2 contained an acrylic/styrene acryliclatex binder from Rohm & Haas (RHOPLEX P-376 binder). The SRS-II aluminawas purchased from Grace. The BET surface area of this material was ca.300 m²/g and it contained approximately 5% silica. The mean particlesize was approximately 7.5 um as measured by a Horiba LA-500 LaserDiffraction Particle Size Distribution Analyzer. The alumina overcoatwas applied at a loading of ca. 0.22 g/in³ of radiator volume. The MnO₂catalyst loadings were approximately 0.44 g/in³ of radiator volume.

The coated radiator was placed within an air duct and subjected to longterm aging in the presence of continuous ambient airflow. The airflowentering the radiator was maintained at an approximate 9.5 mph linearvelocity (ca. 600,000/h radiator space velocity). The radiator washeated internally with hot recirculating coolant (50:50 mixture ofantifreeze and water), and the coolant temperature entering the radiatorwas maintained between 70 and 90° C. depending on the ambient airtemperature. Because of low ambient air temperature, a fraction of theair exiting the radiator was recirculated back to the radiator inlet inorder to maintain the radiator coolant temperature between 70 and 90° C.

Ozone conversion of the four different catalyst compositions wasmeasured periodically to assess any deactivation in performance overtime. This was accomplished by placing the radiator in a different testrig (air duct system) than was used to complete the long-term aging.Ozone conversion was measured at three different airflows correspondingto radiator space velocities of 200,000, 400,000 and 600,000/h.Additionally, ozone conversion was measured at three differenttemperature conditions (“90° C.”, “75° C.”, and 45° C.). For the 90° C.temperature condition, the radiator test rig was operated in“single-pass” airflow mode where 100% of the air entering the radiatorwas fresh ambient air. In this configuration the coolant temperature tothe radiator was maintained at 90° C. The ambient air entering theradiator was preheated to ca. 20-40° C. with an air pre-heater (in orderto achieve the 90° C. coolant temperature), and the air temperatureexiting the radiator was allowed to vary as the airflow was changedduring the ozone conversion measurements (i.e. the higher the airflowthe lower the air temperature). For the other temperature conditionsused to measure ozone destruction performance, the test rig was operatedin “full circulation” airflow mode where the air exiting the radiatorwas recirculated back to the radiator inlet. In this configuration, theair exiting the radiator was maintained at a constant 45 or 75° C. whileozone conversion measurements were taken at different airflows.

Initial conversion results for the four catalyst coating formulationsare shown in Table 1. Initial conversions for Sections 1, 3, and 4 werevirtually identical (e.g., 85% at 600,000/h space velocity and the 90°C. coolant condition), but the overcoated sample of Section 2 was ca. 6%lower (78%, respectively). The radiator was aged for 14 days at ambienttemperature conditions (i.e. the coolant heaters were turned off) andthen the radiator was aged an additional 25 days at normal operatingtemperature (i.e. 70-90° C.). Ozone conversion results at the completionof aging are shown in Table 2.

After aging, the section 3 coating containing the non-preferredreference catalyst formulation typically had the lowest conversion (e.g.37% at 600,000/h space velocity and the 90° C. coolant temperaturecondition). Section 4 containing the small particle catalyst formulationwas a little better (41%, respectively), and Section 1 containing thelarger particle catalyst formulation was better yet (46%, respectively).Section 2 with the overcoated catalyst formulation, however, wassignificantly better (65%, respectively). At the 90° C. temperature testcondition and a space velocity of 600,000/h, the Section 2 catalystformulation lost only an absolute 13% in ozone conversion activityduring the entire aging period while the other three lost at least anabsolute 40% (Table 3). Clearly the SRS-II alumina overcoat on Section 2had a dramatic effect on improving the long-term durability of the MnO₂catalyst underneath. This is particularly significant since the initialactivity of this section was less due to the presence of the overcoat.Despite a reduction in initial activity, the long-term activitymaintenance was excellent.

TABLE 1 Tempera- Space Ozone Conversion (%) ture (C.) Velocity (/h)Section 1 Section 2 Section 3 Section 4 90 600,000 85.0 78.3 84.5 85.0400,000 91.4 86.4 90.9 90.7 200,000 95.5 92.9 98.9 95.3 75 600,000 92.885.6 92.4 88.0 400,000 94.7 91.0 94.7 92.1 200,000 97.2 95.2 97.6 96.745 600,000 82.2 73.1 81.9 80.1 400,000 89.4 82.8 89.1 87.1 200,000 96.893.2 96.4 95.0

TABLE 2 Tempera- Space Ozone Conversion (%) ture (C.) Velocity (/h)Section 1 Section 2 Section 3 Section 4 90 600,000 46.1 65.0 37.0 41.0400,000 53.7 73.0 45.0 50.5 200,000 74.4 87.5 65.5 74.4 75 600,000 42.762.9 33.4 38.3 400,000 49.0 70.0 39.9 44.6 200,000 67.1 84.0 58.3 59.945 600,000 25.4 46.2 21.3 22.5 400,000 32.3 55.5 26.4 27.0 200,000 49.975.5 42.2 39.2

TABLE 3 Ozone Conversion %^(a) Section 1 Fresh 85.0 Section 1 Aged 46.1Section 2 Fresh 78.3 Section 2 Aged 65.0 Section 3 Fresh 84.5 Section 3Aged 37.0 Section 4 Fresh 85.0 Section 4 Aged 41.0 ^(a)Ozone ConversionTest Conditions: 90° C. Coolant Temperature, 600,000/hr Space Velocity,ca 200 ppb ozone.

EXAMPLE 2

Volvo S-70 and S-70T (turbo) radiators were coated in three separatesections (“stripes”) with three MnO₂ based ozone destroying catalystformulations. A brief description of each formulation is given below:

Section 1: 3.5 μm average particle size MnO₂ coating containing asilicone/acrylic binder blend and overcoated with SRS-II alumina.

Section 2: same as Section 1 formulation without the alumina overcoat.

Section 3: 3.5 μm average particle size MnO₂ coating containing anEVA/acrylic binder blend and overcoated with SRS-II alumina.

The MnO₂ binder system used in the Section 1 and 2 formulationscontained a 3:1 blend of acrylic/styrene acrylic latex binder (RHOPLEXP-376 from Rohm & Haas) with a reactive silicone latex binder resin(M-50E from Wacker Silicones Corp.). The MnO₂ binder system used in theSection 3 formulation contained a 1:1 blend of acrylic/styrene acryliclatex binder (RHOPLEX P-376 from Rhom & Haas) with an EVA (ethylenevinyl acetate) latex binder from National Starch (DUROSET Elite 22). TheSRS-II alumina binder system used in the overcoat formulations coated inSections 1 and 3 contained only the acrylic/styrene acrylic latex binder(RHOPLEX P-376) from Rohm & Haas. The SRS-II alumina was purchased fromGrace. The BET surface area of this material was ca. 300 m²/g and itcontained approximately 5% silica. The mean particle size wasapproximately 6.5 um as measured by a Horiba LA-500 Laser DiffractionParticle Size Distribution Analyzer. The alumina overcoats were appliedat loadings of ca. 0.18 g/in³ of radiator volume. The MnO₂ catalystloadings were approximately 0.35 g/in³ of radiator volume.

The coated radiators were placed on Volvo S-70 and S-70 T (turbo)vehicles and subjected to accelerated on-road mileage accumulation (ca.1,000 miles per day). The radiators of both vehicles were removed afteraccumulating approximately 16,000 miles in the Detroit, Mich.metropolitan area during February 1999. The ozone conversion of thecoated sections on each radiator was evaluated to assess anydeactivation in performance over time. The radiators were thenre-installed on the vehicles, and an additional 16,000 miles wasaccumulated on each (32,000 total miles) in the Phoenix, Ariz.metropolitan area during March 1999. The radiators were once againremoved, and the ozone conversion of the coated sections on eachradiator was evaluated to further assess any deactivation in performanceover time. Finally, the radiators were re-installed on the vehicles, andan additional 18,000 miles was accumulated on each (50,000 total miles)in the Phoenix, Ariz. metropolitan area during April 1999. The radiatorswere removed one last time, and the ozone conversion of the coatedsections on each radiator was evaluated to further assess anydeactivation in performance over time.

Ozone conversion was measured by placing the radiators in a full-scaleradiator test rig (air duct), heating the radiators internally with hotrecirculating coolant (50:50 mixture of antifreeze and water), andblowing ozone-containing air over the radiators. Ozone conversion wasmeasured at three different airflows corresponding to radiator spacevelocities of 200,000, 400,000, and 600,000/h. Additionally, theradiator test rig was operated to achieve three different temperatureconditions (90° C., 75° C., and 45° C.). For the 90° C. condition, thetest rig was operated in “single-pass” airflow mode where 100% of theair entering the radiator was fresh ambient air. In this configurationthe coolant temperature to the radiator was maintained at 90° C. Theambient air entering the radiator was preheated to ca. 20° C. to 40° C.(in order to maintain the 90° C. coolant temperature), and the airtemperature exiting the radiator was allowed to vary as the airflow waschanged during the ozone conversion measurements (i.e. the higher theairflow the lower the air temperature). For the other temperatureconditions used to measure ozone destruction performance, the test rigwas operated in “full recirculation” airflow mode where the air exitingthe radiator was recirculated back to the radiator inlet. In thisconfiguration, the air exiting the radiator was maintained at a constant45 or 75° C. while ozone conversion measurements were taken at differentairflows.

Ozone conversion results fresh and after on-road aging for the threeformulations on the S-70 radiator are shown in Tables 4-8. Although bothof the alumina-overcoated sections had initial lower conversions, thesesections showed substantially less decline in conversion with on-roadaging. In fact, as illustrated in Table 8, the overcoated Section 3catalyst formulation showed virtually no deactivation over 51,000 mileswhereas the non-overcoated Section 2 catalyst lost an absolute 23% inozone conversion. Although, ozone conversion for the three sections wasvirtually identical after 32,000 miles, after 51,000 miles, both of theovercoated catalyst formulations on Sections 1 and 3 had significantlybetter ozone conversion than the non-overcoated catalyst formulation onSection 2. Additional on-road aging would be expected to result incontinued faster deactivation for the non-overcoated formulationrelative to the two overcoated formulations.

TABLE 4 Volvo S-70 Fresh Temperature Ozone Conversion (%) (C.°) SpaceVelocity (/h) Section 3 Section 2 Section 1 90 600,000 48.4 61.9 53.3400,000 53.9 68.5 61.0 200,000 65.5 80.2 71.6 75 600,000 52.6 65.8 58.3400,000 58.3 72.3 64.2 200,000 70.3 80.0 75.0 45 600,000 41.7 51.4 43.5400,000 47.1 61.6 50.2 200,000 63.4 74.5 67.5

TABLE 5 Volvo S-70 aged 16,140 miles Temperature Ozone Conversion (%)(C.°) Space Velocity (/h) Section 3 Section 2 Section 1 90 600,000 49.751.9 51.7 400,000 55.0 61.5 60.0 200,000 67.7 74.3 71.4 75 600,000 50.850.8 50.6 400,000 55.8 59.7 58.3 200,000 72.4 76.3 73.7 45 600,000 45.649.6 45.3 400,000 50.8 52.0 50.1 200,000 63.2 68.1 65.8

TABLE 6 Volvo S-70 aged 32,087 miles Temperature Ozone Conversion (%)(C.°) Space Velocity (/h) Section 3 Section 2 Section 1 90 600,000 47.645.7 46.7 400,000 53.1 51.6 53.4 200,000 65.9 65.6 65.6 75 600,000 48.344.1 47.3 400,000 57.0 54.9 56.9 200,000 71.4 67.9 69.5 45 600,000 44.736.9 38.3 400,000 48.8 43.9 46.1 200,000 64.7 57.4 60.0

TABLE 7 Volvo S-70 aged 50,863 miles Temperature Ozone Conversion (%)(C.°) Space Velocity (/h) Section 3 Section 2 Section 1 90 600,000 47.539.0 43.9 400,000 54.2 49.6 53.0 200,000 67.8 63.0 67.2 75 600,000 49.939.5 47.0 400,000 60.3 49.9 54.7 200,000 71.3 62.0 70.5 45 600,000 41.226.2 29.9 400,000 47.3 33.3 40.0 200,000 60.8 46.9 55.5

TABLE 8 Ozone Conversion %^(b) Section 1 Fresh 53.3 Section 1 Aged16,140 miles 51.7 Section 1 Aged 32,087 miles 46.7 Section 1 Aged 50,863miles 43.9 Section 2 Fresh 61.9 Section 2 Aged 16,140 miles 51.9 Section2 Aged 32,087 miles 45.7 Section 2 Aged 50,863 miles 39.0 Section 3Fresh 48.4 Section 3 Aged 16,140 miles 49.7 Section 3 Aged 32,087 miles47.6 Section 3 Aged 50,863 miles 47.5 ^(b)Ozone Conversion TestConditions: 90° C. Coolant Temperature; 600,000 (1/hr) Space Velocity;ca. 200 ppb ozone

Similar fresh and aged ozone conversion results for the same threeformulations coated on the S-70 T radiator are shown in Tables 9-13.Although all sections showed some decline in activity with on-roadaging, the overcoated sections declined at a significantly slower rate.In fact, as illustrated in Table 13, the overcoated Section 1 and 3catalyst formulations showed an absolute loss in ozone conversion ofapproximately 13% after 50,000 miles whereas the non-overcoated Section2 catalyst lost an absolute 22% in ozone conversion. In addition, after50,000 miles, both of the alumina overcoated catalyst formulations(particularly the Section 3 catalyst) had higher ozone conversion thanthe non-overcoated catalyst formulation. Additional on-road aging wouldbe expected to result in continued faster deactivation for thenon-overcoated formulation relative to the two overcoated formulations.

TABLE 9 Volvo S-70T Fresh Temperature Ozone Conversion (%) (C.°) SpaceVelocity (/h) Section 3 Section 2 Section 1 90 600,000 67.2 67.0 60.5400,000 75.8 73.7 68.2 200,000 85.1 85.4 82.0 75 600,000 62.4 60.7 53.2400,000 68.3 67.3 62.7 200,000 83.1 82.9 80.2 45 600,000 53.0 50.7 43.6400,000 62.3 61.2 55.4 200,000 77.4 76.2 72.2

TABLE 10 Volvo S-70T aged 16,233 miles Temperature Ozone Conversion (%)(C.°) Space Velocity (/h) Section 3 Section 2 Section 1 90 600,000 56.850.5 51.1 400,000 63.7 60.1 59.5 200,000 81.8 78.6 77.4 75 600,000 57.454.2 52.2 400,000 65.0 61.8 60.8 200,000 80.4 77.7 77.0 45 600,000 47.642.5 40.2 400,000 56.5 50.7 50.3 200,000 74.7 69.5 69.8

TABLE 11 Volvo S-70T aged 32,277 miles Temperature Ozone Conversion (%)(C.°) Space Velocity (/h) Section 3 Section 2 Section 1 90 600,000 57.748.1 48.7 400,000 63.6 57.4 58.3 200,000 76.9 71.5 72.4 75 600,000 56.950.4 50.3 400,000 67.2 59.2 60.5 200,000 79.8 71.7 73.9 45 600,000 48.437.8 38.0 400,000 50.9 46.0 44.6 200,000 66.8 59.3 58.7

TABLE 12 Volvo S-70T aged 50,173 miles Temperature Ozone Conversion (%)(C.°) Space Velocity (/h) Section 3 Section 2 Section 1 90 600,000 54.445.0 46.9 400,000 61.7 52.0 53.4 200,000 78.0 69.9 72.0 75 600,000 55.943.1 46.6 400,000 64.1 51.5 55.8 200,000 80.0 69.4 74.4 45 600,000 42.029.9 32.3 400,000 49.4 37.3 42.5 200,000 67.1 53.8 59.8

TABLE 13 Ozone Conversion %^(c) Section 1 Fresh 60.5 Section 1 Aged16,233 miles 51.1 Section 1 Aged 32,277 miles 48.7 Section 1 Aged 50,173miles 46.9 Section 2 Fresh 67.0 Section 2 Aged 16,233 miles 50.5 Section2 Aged 32,277 miles 48.1 Section 2 Aged 50,173 miles 45.0 Section 3Fresh 67.2 Section 3 Aged 16,233 miles 56.8 Section 3 Aged 32,277 miles57.7 Section 3 Aged 50,173 miles 54.4 ^(c)Ozone Conversion TestConditions: 90° C. Coolant Temperature; 600,000 (1/hr) Space Velocity;ca. 200 ppb ozone.

EXAMPLE 3

A Ford TAURUS automobile radiator was coated in three separate sections(“stripes”) with three MnO₂ based ozone destroying catalystformulations. A brief description of each formulation is given below:

Section 1: 3.5 μm average particle size MnO₂ coating containing anEVA/acrylic binder blend and overcoated with SRS-II alumina.

Section 2: same as Section 1 formulation without the alumina overcoat.

Section 3: 3.5 μm average particle size MnO₂ coating containing anEVA/acrylic binder blend and overcoated with SRS-II alumina and furtherovercoated with FC-824 water repellent.

The MnO₂ binder system used in all sections contained a 1:1 blend ofacrylic/styrene acrylic latex binder (RHOPLEX P-376 binder from Rhom &Haas) with an EVA (ethylene vinyl acetate) latex binder from NationalStarch (DUROSET Elite 22 binder). The SRS-II alumina binder system usedin the overcoat formulations coated in Sections 1 and 3 contained onlythe acrylic/styrene acrylic latex binder (RHOPLEX P-376 binder) fromRohm & Haas. The SRS-II alumina was purchased from Grace. The BETsurface area of this material was ca. 300 m²/g and it containedapproximately 5% silica. The mean particle size was approximately 6.5 umas measured by a Horiba LA-500 Laser Diffraction Particle SizeDistribution Analyzer. The alumina overcoats were applied at loadings ofca. 0.22 g/in³. The MnO₂ catalyst loadings were approximately 0.38 g/in³of radiator volume.

The FC-824 water repellent was purchased from 3M Corporation, and itcomprised a proprietary fluoropolymer latex emulsion in water. Thisemulsion was diluted to 2.5% solids in water and was subsequentlysprayed onto the Section 3 catalyst formulation such that the catalystcoating was thoroughly wetted. Excess solution was then removed with anairknife, and the entire radiator was then dried at 90° C. forapproximately 1 hour.

The coated radiator was placed on a Ford TAURUS vehicle and subjected toaccelerated on-road mileage accumulation (ca. 1,000 miles per day). Theradiator was removed after accumulating 18,000 miles in the Phoenix,Ariz. metropolitan area during April 1999. The ozone conversion of thecoated sections on the radiator was evaluated to assess any deactivationin performance over time. The radiator was then re-installed on thevehicle, and an additional 18,000 miles was accumulated (36,000 totalmiles) in the Phoenix, Ariz. metropolitan area during May 1999. Theradiator was once again removed, and the ozone conversion of the coatedsections on the radiator was evaluated to further assess anydeactivation in performance over time. Finally, the radiator wasreinstalled on the vehicle, and an additional 14,000 miles wasaccumulated (50,000 total miles) in the Detroit, Mich. metropolitan areaduring June 1999. The radiator was removed one last time, and the ozoneconversion of the coated sections on the radiator was evaluated tofurther assess any deactivation in performance over time.

Ozone conversion was measured by the same procedure described inExamples 1 and 2.

Ozone conversion results fresh and after on-road aging for the threeformulations on the Ford Taurus radiator are summarized in Table 14.Although all sections showed some decline in activity with on-roadaging, the two overcoated sections declined at a slower rate. Asillustrated in Table 14, the overcoated Section 1 and 3 catalystformulations showed an absolute loss in ozone conversion of 15 and 8%,respectively, after 50,000 miles whereas the non-overcoated Section 2catalyst lost an absolute 19% in ozone conversion. Clearly, theovercoated catalyst formulations, particularly the Section 3 catalystformulation with the combination of alumina and water repellent,deactivated the least after 50,000 miles of on-road aging. In addition,both of the overcoated catalyst formulations had higher ozone conversionafter 50,000 miles aging than the non-overcoated catalyst formulation.Additional on-road aging would be expected to result in continued fasterdeactivation for the non-overcoated formulation relative to the twoovercoated formulations.

TABLE 14 Ozone Conversion %^(d) Section 1 Fresh 84.4 Section 1 Aged18,506 miles 77.0 Section 1 Aged 36,168 miles 74.7 Section 1 Aged 50,335miles 69.0 Section 2 Fresh 84.7 Section 2 Aged 18,506 miles 81.1 Section2 Aged 36,168 miles 77.0 Section 2 Aged 50,335 miles 65.7 Section 3Fresh 76.5 Section 3 Aged 18,506 miles 70.8 Section 3 Aged 36,168 miles73.0 Section 3 Aged 50,335 miles 68.4 ^(d)Ozone Conversion TestConditions; 90° C. Coolant Temperature; 600,000 (1/hr) Space Velocity;ca. 200 ppb ozone.

What is claimed:
 1. A method for treating the atmosphere tocatalytically convert atmospheric pollutants to less harmful materialscomprising contacting the pollutant containing atmosphere with astationary surface which has been coated with a catalyst compositionselected from base metals, precious metals, salts and oxides thereof andcombinations thereof, the catalyst composition being protected with anovercoat of at least one porous protective material selected fromcarbon, zeolites, clays, alumina, high surface area silica containingaluminum oxide, silica containing high surface area alumina, titania,zirconia, silica, rare earth oxides and mixtures thereof, saidprotective material is sufficiently porous to enable said atmospherecontaining said pollutants to pass therethrough into operative contactwith the catalyst composition and sufficiently protective tosubstantially prevent catalyst degrading pollutants from contacting thecatalyst composition.
 2. The method of claim 1 wherein said stationarysurface is selected from billboards, road signs and outdoor heating,ventilating and air conditioning equipment.
 3. The method of claim 1wherein said atmospheric pollutants to be converted are selected fromozone, hydrocarbons, carbon monoxide and mixtures thereof.
 4. The methodof claim 1 wherein said catalyst composition is selected from manganesedioxide, platinum, palladium and mixtures thereof and said porousprotective material is selected from alumina, silica and mixturesthereof.
 5. The method of claim 1 wherein the catalyst composition issupported on a material selected from ceria, alumina, titania, silica,zirconia and mixtures thereof.
 6. The method of claim 1 furthercomprising coating the porous protective material overcoated catalyticsurface with at least one hydrophobic protective substance which iscapable of substantially preventing liquid water and/or water vapor fromreaching the catalyst composition.
 7. The method of claim 6 wherein thehydrophobic substance is selected from the group comprisingfluoropolymers and silicone polymers.
 8. The method of claim 1 whereinthe catalyst composition comprises manganese dioxide.
 9. The method ofclaim 1 wherein the porous protective material is alumina and thecatalyst composition comprises manganese dioxide.
 10. The methodaccording to claim 1, wherein said method is performed at a temperatureof from about 0 to about 150° C.
 11. A method for treating theatmosphere to catalytically convert atmospheric pollutants to lessharmful materials comprising contacting the pollutant containingatmosphere with a stationary surface which has been coated withencapsulated particles of a catalyst composition said catalystcomposition selected from base metals, precious metals, salts and oxidesthereof and combinations thereof, said particles having been protectedby encapsulation prior to their use for coating said surface with atleast one porous protective material selected from carbon, zeolites,clays, alumina, high surface area silica containing aluminum oxide,silica containing high surface area alumina, titania, zirconia, silica,rare earth oxides and mixtures thereof said protective material issufficiently porous to enable said atmosphere containing said pollutantsto pass therethrough into operative contact with the catalystcomposition and sufficiently protective to prevent catalyst degradingpollutants from contacting the catalyst composition.
 12. The method ofclaim 11 wherein said stationary surface is selected from billboards,road signs and outdoor heating, ventilating and air conditioningequipment.
 13. The method of claim 11 wherein said atmosphericpollutants to be converted are selected from ozone, hydrocarbons, carbonmonoxide and mixtures thereof.
 14. The method of claim 11 wherein saidcatalyst composition is selected from manganese dioxide, platinum,palladium and mixtures thereof and said porous protective material isselected from alumina, silica and mixtures thereof.
 15. The method ofclaim 11 wherein the catalyst composition is supported on a materialselected from ceria, alumina titania, zirconia and mixtures thereof. 16.The method of claim 11 further comprising coating the porous protectivematerial overcoated catalytic surface with at least one hydrophobicprotective substance which is capable of substantially preventing liquidwater and/or water vapor from reaching the catalyst composition.
 17. Themethod of claim 16 wherein the hydrophobic substance is selected fromthe group comprising fluoropolymers and silicone polymers.
 18. Themethod of claim 11 wherein the catalyst composition comprises manganesedioxide.
 19. The method of claim 11 wherein the porous protectivematerial is alumina and the catalyst composition comprises manganesedioxide.